1. The Field of the Invention
The invention relates to blast wave absorption systems and more specifically to blast wave absorption systems that effectively suppress Mach reflections of a supersonic blast wave.
2. The Relevant Technology
When a bomb or other explosive device is detonated, the area around the explosion becomes overpressurized, resulting in highly compressed air particles that travel outward from the explosion at a high rate of speed, thereby forming a blast wave. This blast wave will dissipate over time and distance and will exist generally only for a matter of milliseconds at any one distance from the explosion. However, in that short amount of time the blast wave can create a tremendous amount of force against anything with which it comes in contact, typically causing a great deal of damage. Furthermore, a transonic flow can follow the shock wave front, which causes a secondary force that can also cause damage.
The faster a blast wave propagates the more damage it potentially can inflict. At the speed of sound in the air (Mach (M)=1 or approximately 330 m/s) the equivalent excess pressure caused by the blast wave is close to 0.6 bars. This pressure is dangerous for most buildings, but typically not sufficient to damage an armored vehicle. At larger blast wave velocities (i.e., at supersonic speeds (M>1)), however, the waves become damaging to practically any man-made structure.
To protect against such a blast wave, devices have been designed to absorb the energy caused by these blast waves. Some typical areas where the energy absorbing devices have been used include explosive ordnance disposal (EOD) suits, vehicle armor, supersonic aircraft engine linings, and building protection. One feature that is common to these current designs is the use of energy absorbing elements. One example of a current use of an energy absorbing element is a blast door. The typical blast door is suspended on springs so that the springs can absorb the impact energy when the blast wave hits the door. Another example is chalk panels, which fracture on impact and friction between the particles absorbs energy. Another energy absorbing scheme is described in U.S. Pat. No. 6,200,664, where energy is absorbed by liquid contained within collapsible structures. Still another example is described in U.S. Pat. No. 7,017,705, which deals with incident and reflected waves by incorporating an evacuated layer in a wave-absorbing device.
While energy absorbing devices have been effective for blast waves traveling at lower velocities, they have not been able to withstand the higher velocity blast waves. What is needed in the art, therefore, are systems that can increase dissipation or deflection of the higher velocity blast waves, with or without the use of energy absorbing materials or devices.